1. Field of the Invention
The present invention relates to a cooling jacket for an electric motor and a motor unit having a cooling jacket mounted on an electric motor.
2. Description of Related Art
There have been developed various cooling structures for cooling an electric motor by providing passages of coolant such as water at a circumference of the electric motor.
As one of these structures, a structure for cooling an electric motor by coolant passages formed in an outer casing of the electric motor is known from JP 5-103445A, JP 9-285072A, JP 2002-119019A, for example. Further, an electric motor with cooling structure in which a cooling jacket for flowing coolant is arranged between a frame and a stator core of the electric motor is known from JP 2001-45701A.
In the structure where coolant passages are formed in the outer casing of the electric motor, it is necessary to machine the coolant passages in the casing of the electric motor so that a large number of machining processes is required to increase the manufacturing cost. Regarding the structure where the cooling jacket having coolant passages is arranged between the frame and the stator core, this structure is complicated and requires a large number of manufacturing processes to increase the manufacturing cost.
Further, there is known an electric motor in which a jacket having coolant passages is arranged around a cylindrical outer frame of an electric motor and is fastened at both ends by fasteners to be fit to the outer frame, and liquid synthetic resin mixed with adhesive or aluminum powder is filled between the jacket and the outer frame to expedite heat conduction in between, as disclosed in JP 9-201000A and JP 9-201010A.
In this structure, the jacket has to be prepared specific to the electric motor to increase the manufacturing cost. Further, it is possible to fasten the jacket onto the electric motor having a cylindrical outer frame in close contact therewith, but it is difficult to fasten the jacket closely onto an outer frame of a shape other than a cylindrical shape. Even in a case of the electric motor having the cylindrical frame, if the jacket abuts on the outer frame not evenly, close contact of the jacket and the outer frame is greatly decreased.